WASHINGTON — Scott Seymour, president and chief executive of Aerojet Rocketdyne, abruptly retired from the company June 1 and has been replaced by an executive who joined the company only three months ago.

Neither the 64-year-old Seymour nor the company offered an explanation for his sudden retirement, announced by the company June 1. According to a filing with the U.S. Securities and Exchange Commission June 1, Seymour announced his intent to retire May 29. “Seymour’s resignation was not the result of any disagreement related to any matter involving the Company’s operations, policies or practices,” the filing stated.

Warren Lichtenstein, chairman of the company’s board of directors, praised Seymour. “Scott was instrumental in our 2013 acquisition of Pratt & Whitney Rocketdyne, a bold move that merged two industry giants and has been pivotal in securing the future growth of our company in a challenging marketplace,” he said in a June 1 statement.

A former Northrop Grumman executive, Seymour joined the company in 2010 as president and chief executive of Aerojet’s parent company, then known as GenCorp and recently renamed Aerojet Rocketdyne Holdings, Inc. In February, he replaced Warren M. Boley, Jr. as president of Aerojet Rocketdyne.

In March, he approved a consolidation plan that calls for reducing the company’s workforce by 10 percent over the next several years. Those cuts were intended “to improve the affordability of our products,” he said in a statement at the time.

Replacing Seymour as president and chief executive is Eileen Drake, who joined the company as its chief operating officer in early March. Drake, a former U.S. Army aviator, previously worked for more than a decade at United Technologies Corp., including serving as president of a Pratt & Whitney AeroPower business unit from 2012 to January 2015.

“Her leadership will be instrumental in positioning our organization for continued growth and increased profitability,” Lichtenstein said, adding that Drake and Seymour would “work closely together to ensure a smooth transition.”

The change in leadership comes as Aerojet Rocketdyne faces major challenges in its space propulsion business. After the loss of an Antares rocket in October 2014, powered by AJ-26 engines from Aerojet Rocketdyne, Orbital ATK announced it was replacing the AJ-26 with RD-181 engines from Russian firm NPO Energomash. The results of separate investigations into the accident by both Aerojet Rocketdyne and Orbital ATK have yet to be released.

Aerojet Rocketdyne is also seeking funding for the AR-1, a large engine intended to replace the RD-180 engine from NPO Energomash currently used on the United Launch Alliance Atlas 5. However, ULA’s preferred choice for a new engine is the BE-4 from Blue Origin, which ULA plans to use in the first stage of its new Vulcan launch vehicle.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...